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This is a National Transportation Safety Board 
special investigation report dealing with the safe 
transportation of hazardous materials. Your comments 
about the format, contents and usefulness of the report 
would provide helpful guidance for future special 
investigation reports issued by the Safety Board. We 
also invite your suggestions for ways to make these 
reports more helpful to you in your efforts to improve 
transportation safety. 

Please address your comments to: 

Managing Director, MD-1 

National Transportation Safety Board 

Washington, D.C. 20594 


1 . Report No. 


2. Government Accession No. 

k. Title and Subt i tie 

Special Investigation Report: An Overview of a 
Bulk Gasoline Delivery Fire and Explosion 

3 • Reci pi ent ' s Catalog No. 

5. Report Date 

February 24, 1978 

6 . Perform! ng Organization 

8. Performing Organization 
Report No. 

7. Author(s, 

9. Performing Organization Name and Address 
National Transportation Safety Board 
Bureau of Technology 
Washington, D.C. 20594 

10. Work Unit No. 

11. Contract or Grant No. 

I 2. Sponsor i ng Agency Name and Address 

Washington, D. C. 20594 

13-Type of Report and 
Period Covered 

Special Investigation 

1 k . Sponsor i ng Agency Code 

1 5 ■ Suppl ementary Notes 

16. Abstract 

This special investigation examined safeguards against fire and explosion during 
gasoline deliveries at service stations with aboveground storage tanks. The investi- 
gation included a critical review of a serious fire and explosion which killed 3 
firemen, injured 28 persons, and caused losses of $4,000,000. Principal factors 
discussed are the effect of unimplemented safety codes, and maintenance or misuse 
of safety features on equipment being used to deliver gasoline at service stations. 
Recommendations are made to reduce the effect of unimplemented codes, to stimulate 
improved maintenance of safety features on gasoline cargo tanks and to improve 
gasoline transportation safety standards administration. Recommendations are made 
to the Fire Marshals Association of North America, the American Association of Motor 
Vehicle Administrators, and the Underwriters Laboratories, Inc. 

17. Key Words 

Hazardous materials fire; explosion; storage tank; 
gasoline; injury; emergency response; highway carrier; 
terminal operator. 

IS-Security Classification 
(of this report) 

20. Security Classification 
(of this page) 

1 8 .Di stri but ion Statement 

This document is available 
to the public through the 
National Technical Informa- 
tion Service, Springfield, 
Virginia 22151 

21 .No. of Pages 


22. Price 

NTSB Form 1765.2 (Rev. 9/74) 





The Accident 3 

Storage Tank 6 

Transfer Equipment 8 

Tank Vehicle 9 


Relaxation of Codes or Standards 10 

Maintaining Tank Vehicles to Safety Standards 13 

UL-Listed Equipment — Misuse and Modification .... 13 

Administrative Provisions in Safety Codes and Standards . 14 




Appendix A - Acknowledgments 19 

Appendix B - Excerpts from Flammable and Combustible 

Liquids Code NFPA No. 30-1973 20 

Appendix C - Summary of Events and Enabling Factors, 
Gasoline Delivery, Fire and Explosion, 

Gadsden, Alabama, August 31, 1976. ... 25 

WASHINGTON, D. C. 20594 


Adopted: February 24, 1978 



Gasoline is transported in greater quantities than any other hazardous 
material. Most gasoline is distributed through service stations that serve 
the public and arrives at these stations by tank vehicles, usually tank 
semitrailers; it is transferred from the vehicle into underground or above- 
ground storage tanks. Accidents over the years have demonstrated how 
dangerous these transfers can be, and have precipitated the development of 
extensive safety codes and standards to lessen these dangers. 

Despite the safety codes and standards, accidents continue; during 
1977, gasoline unloading accidents in Kentucky, Georgia, Minnesota, and 
New York were reported to the U.S. Department of Transportation (DOT). 
Other accidents have occurred which were not reported to the DOT, because 
the transportation of gasoline was under the jurisdiction of individual 
States. One of these accidents occurred on August 31, 1976, when a fire 
erupted while a truckdriver was making a gasoline delivery from his 
tractor-semitrailer (tank) into an aboveground storage tank at a service 
station near Gadsden, Alabama; the fire and an explosion resulted in the 
deaths of 3 firefighters, injuries to 11 other firefighters and 17 
bystanders, and caused an estimated $4,000,000 loss. (See figure 1.) 

The State of Alabama Fire Marshal's Office investigated the fire 
and explosion to determine the cause. After participating in and 
reviewing that investigation, the Safety Board undertook a special 
investigation to determine how this delivery accident could result in 
such large losses in view of existing safety codes and standards, and 
to determine if these circumstances represent broader safety problems 
affecting gasoline transportation safety nationwide. The investigation 
disclosed that important safeguards prescribed in safety codes and 
standards had not been implemented at Gadsden, that these circumstances 
are not unique to the Gadsden accident, and that both safeguards and the 
administration of safety codes and standards can be improved to reduce 
risks of future gasoline delivery fires and explosions. 

Recommendations based on the findings of this investigation were 
made to the Fire Marshals Association of North America, the American 
Association of Motor Vehicle Administrators, and the Underwriters 
Laboratories, Inc. 

- 2 - 

- 3 - 


The following reconstruction of events at Gadsden has been compiled 
from the deputy fire marshal's report and other information made available 
to the Safety Board during its special investigation. 

The Accident 

Sometime before 2 p.m., on August 31, 1976, a truckdriver for the 
Martin Oil Coiftpany, Inc., (Martin) arrived with his gasoline-laden 
tractor-semitrailer (tank) at a Martin service station near Gadsden. 
The driver was to deliver 3,800 gallons of premium gasoline and 3,600 
gallons of regular gasoline to the station. The station had two 6,000- 
gallon, steel, aboveground gasoline storage tanks. (See figure 2.) He 
parked his trailer about 3 feet from storage tank No. 1 and about 10 feet 
from storage tank No. 2. (See figure 3.) He measured 4 inches of 
gasoline remaining in storage tank No. 2, into which he was to make his 
delivery of premium gasoline, and repositioned the cap over the opening 
through which he made his measurement. After a cursory inspection of 
the tank, he took an electric transfer pump and hoses out of the compart- 
ment under his trailer and connected the pump between the trailer and the 
storage tank fill connection. Next, he plugged the pump's electrical 
cord into an outdoor receptacle between the two storage tanks. (See 
figure 2.) He then went inside the station and closed the electrical 
switch. After returning to the trailer, the driver operated the control 
valves to start the flow of gasoline. He did not notice anything abnormal 
about the fuel transfer equipment. 

As the liquid level in the storage tank rose above the pipe which 
leads from the bottom of the tank to the dispensing unit, gasoline began 
to leak through a crack in a brass, 1 1/2-inch gate valve at the bottom 
of the tank. The driver, who was busy with his unloading tasks at the 
truck, did not notice the leak. 

As the tank continued being filled, gasoline leaked more rapidly 
because of the increased hydrostatic pressure at the bottom of the tank. 
The escaping gasoline flowed for almost 20 minutes onto the gravel-covered 
ground between the storage tank and the trailer where the transfer pump 
was operating. Some of the gasoline evaporated and formed a vapor-enriched 
atmosphere in the still air. The escaping gasoline continued to increase 
the concentration of gasoline in the air until it exceeded its lower 
flammability limits. The vapors permeated the space between energized 
wires in an electrical junction box without a cover plate at the pump 
motor; the energized wires ignited those vapors. 

The spilled gasoline burned rapidly and engulfed the fuel transfer 
system. Within 5 minutes the rubber discharge hose burned through and 
released gasoline from the trailer which abruptly intensified the fire. 

- 4 - 

- 5 - 

The Gadsden, Glencoe, and Hokes Bluff fire departments received 
alarms at 2:20 p.m., and were at the scene in 5 minutes. On arrival, 
the firefighters saw the intense fire under the trailer and, therefore, 
concentrated their firefighting efforts there. They attacked with two 
1 1/2 -inch hose lines supplied with water by their apparatus tanks. 

The fire was continually fed by gasoline which leaked through the 
cracked brass valve on storage tank No. 2 and by gasoline from the 
trailer. While the firefighters were fighting the fire, the vapor vent 
on storage tank No. 2 began to whistle; the firemen also saw a 35-foot 
plume of fire extending horizontally from the front of the storage tank 
toward the trailer. Fire engulfed the front end of the storage tank at 
its base, and spread underneath the tank. Heat continued to increase 
pressure inside the storage tank and weaken the wall of the tank. Fire- 
fighters reported small explosions during this stage of the fire. 

At 2:59 p.m., the weld seam between the tank head and the tank body 
split 12 to 14 inches. The split propagated along the weld seam downward 
on the right side and caused more gasoline to spill onto the ground. 
The fire changed to a "low, rich fire" when suddenly the vapors inside 
the tank ignited and the tank exploded. The explosion propelled the 
front tank head into three of the firefighters as it traveled at a 45° 
angle to the longitudinal axis of the tank. This tank head traveled 
over 150 feet farther and struck a truck, a trailer, and a fire department 
pumper before it came to rest. The rest of the tank rocketed 240 feet 
in a southwesterly direction through a pine grove and into a field. 
Storage tank No. 1 was dislodged from its concrete support and came to 
rest 10 feet from its original position. Simultaneously, a 150-foot- 
diameter fireball rose several hundred feet into the air and ignited 
combustibles up to 600 feet away. Three firefighters, including the 
Gadsden fire chief, were killed by the fireball and tank fragment. 
Twenty-eight other persons were injured. 

The resultant fires involved the service station, trailers, other 
vehicles, and brush. These fires were quickly brought under control by 
the surviving firefighters. 

The events sequence was summarized to describe the main events 
leading to the explosion and fireball, to show factors that enabled each 
main event to occur, and to indicate the factors addressed by existing 
safety codes and standards. (See Appendix C.) 

Storage Tank 

The service station was leased by Martin from another company in 
Gadsden. Located on the outskirts of Gadsden, this facility consisted 
of an office building, the two gasoline storage tanks, an underground 
diesel fuel storage tank, a trailer storage facility behind the station, 
and two mobile home trailers. (See figure 3.) 

7 - 

The storage and handling of gasoline at this service station and 
others throughout Alabama are under the jurisdiction of the State fire 
marshal. As in many other States, the State fire marshal, beginning in 
1965, adopted the current editions of the safety codes and standards of 
the National Fire Protection Association (NFPA) for use within Alabama. 
The facility at Gadsden had been in service at least 15 years, but had 
been leased by Martin about 6 months before the accident. When Martin 
began operating the station, NFPA Code No. 30-1973 was in effect. (See 
Appendix B.) Section 1050 of the code states that code provisions "may 
be altered at the discretion of the authority having jurisdiction...." 
Section 1060 of the code states that "existing. . .equipment. .. for the 
storage, handling and use of flammable. .. liquids which are not in strict 
compliance with the terms of this code may be continued in use provided 
they do not constitute a recognized hazard to life or adjoining property." 
These two sections permit the approving authority to relax code provisions 
so that existing stations can remain in use. 

With only a 13-person staff and widespread duties, the Alabama fire 
marshal's NFPA No. 30 code inspection capabilities were limited. Thus, 
inspection priorities were focused on facilities in urban areas of the 

The fire marshal did not require the Martin facility to be inspected 
and approved under the safety code. Therefore, code variances were never 
discussed with the owner or lessee of the station. The fire marshal did 
not consider the station to be in violation of the code. 

The Martin station facilities did not conform with several provisions 
of the NFPA No. 30 code. For example. Section 7111 of the code does not 
permit aboveground gasoline storage tanks at service stations. Delivery 
into aboveground storage tanks at service stations allows less margin 
for error than into underground tank configurations. An aboveground tank 
requires more than a gravity flow system for delivery from the delivering 
transportation vehicle, which introduces a need for additional transfer 
equipment and complicates the driver's unloading tasks. Both increase 
the opportunity for something to go wrong. 

In order to reduce the risks, the NFPA promulgated separate standards 
with additional safeguards for existing aboveground storage tanks, beyond 
those required for underground tanks. For example, these additional safe- 
guards included explosion relief vents, spill control dikes, codes for use 
of an auxiliary electrical transfer pump, and automatic and manual fuel 
shutoff devices on the delivery vehicles. 

The unprotected piping at the bottom of storage tank No. 2 that 
exploded (7212) i' and the use of a brass valve instead of a steel or 

_1/ Numbers in parentheses refer to sections of NFPA code No. 30-1973 in 
Appendix B containing relevant requirements . 

- 8 

modular iron valve in that line (2181, 3130, 3410, and 7210) increased 
the likelihood of gasoline spills. The crack in this brass valve, 
through which gasoline leaked, had resulted from some earlier impact on 
the exposed piping. It could not be determined when or how the piping 
was struck. Examination of the thread run-out area of the valve, upstream 
of the valve seat, indicated that the valve wall was thin in this area 
because of a casting anomaly. 

After the gasoline began to spill, the absence of suitable drains 
or dikes (2170) had several adverse effects. The gasoline and vapors 
flowed through gravel toward the trailer and the pump. This flow 
inhibited detection of the leak by the driver and distributed the gasoline 
into an area containing ignition sources. 

The two storage tanks are Underwriters Laboratories, Inc., (UL) 
"listed." UL's "Standard for Safety No. 142" of 1972 prescribes the 
requirements for construction of steel aboveground tanks for flammable 
liquids including gasoline. When the UL-listed steel storage tank 
breached and exploded, the amount of injury and damages was increased by 
the propulsion of tank fragments and the intense heat from the fireball. 

The firefighters had focused their attention on the burning tank 
vehicle because of the intensity of the fire under it and because of 
their concern about it exploding. The firefighters got as close to the 
trailer as possible to fight the fire, and relied on the normal fill 
vent of the storage tank to relieve any excessive pressure even as the 
vapor vent began to "whistle" and flames spewed from the front of the 
storage tank toward the tractor. They expected the pressure relief 
devices to prevent the tank from rupturing. When the tank ruptured, the 
escaping gasoline was displaced by air, and the tank exploded violently 
shortly thereafter. The firefighters had stayed away from the ends of 
the tank because their previous training led them to believe they would 
be safer on the sides if the tank exploded. However, three firefighters 
were killed when the tank head blew off at an unexpected 45° angle. 

The explosion occurred while the firefighters thought they had the 
fire under control. Thus, firefighters had no apparent reason to flee 
before the explosion. The large fireball also surprised the firefighters 
and bystanders, and contributed to the many injuries. 

Transfer Equipment 

An electrically driven transfer pump and rubber hoses, used to 
unload gasoline into the aboveground storage tank, were carried on the 
tank vehicle. They were hooked up by the driver to enable him to make 
the delivery. There was no evidence to suggest that the pump and hoses 
were not tightly connected before or during the transfer. 

- 9 

Martin conducts business only within the State of Alabama. At the 
time of the accident, Alabama had adopted NFPA Standard No. 385 of 1974 1J , 
which established recommended safety standards for tank vehicles, including 
auxiliary electrical equipment carried on tank vehicles. In addition, UL 
publishes safety standards (79-1967) for pumps and their electrical 
equipment for flammable and combustible liquids. 

The 200-gallon-per-minute pump was a UL-listed product, for use in 
hazardous locations. Class I, Group D and Class II, Group F and G. It 
was designed for permanent installation with fixed wiring. It was supplied 
new with a steel outlet box, a cover plate, and holddown screws designed 
to prevent flammable vapors from entering the box. 

On August 31, 1976, the pump was being used as a portable pump. The 
cover plate and holddown screws were missing, and compacted clay in the 
screw threads of the outlet box indicates that the cover was not in place 
before the accident. This wiring, with a 110-volt potential, was exposed 
to a gasoline-enriched air mixture as gasoline leaked from the tank 
piping, vaporized, and engulfed the area. The location of the first fire 
indicates that it started at this pump. A postaccident inspection of the 
internal motor wiring showed no signs of arcing, and the motor was not 
shut down manually before the driver fled the flames. These factors 
strongly indicate that the fire ignited at the outlet box. 

It could not be determined if the outlet box cover was removed during 
installation of the power cord or during maintenance. The driver was not 
aware of the increased risk created by this modification. 

Tank Vehicle 

Martin is a private intrastate motor truck operator and distributor 
of American Oil Company petroleum products. It serves Etowa and St. Clair 
Counties in Alabama. The operator picks up its bulk petroleum products 
(gasoline, fuel oil, and diesel fuel) with its tank semitrailers at 
Duncan Pipeline Terminal in Birmingham, Alabama. The products are 
transported in the semitrailers directly to service stations near Gadsden, 
if the stations have room for such a delivery, or to Martin's bulk plant. 
Martin operates three tractors, three semitrailers, and two tank trucks; 
it employs five drivers. 

The tank vehicle involved was a 10,000-gallon Trailmobile aluminum 
4-compartment tank semitrailer, manufactured in 1969 to DOT cargo tank 
specification MC-306 (49 CFR 178.341). NFPA Standard No. 385-1974, 
described previously, also contains recommended safety standards for 
such vehicles. 

2^/ "Tank Vehicles for Flammable and Combustible Liquids," National 

Fire Protection Association, Boston, Massachusetts, copyrighted 1975. 

- 10 - 

The cargo tank and appurtenances were certified by the manufacturer 
as being in compliance with the MC-306 specifications. These specifications 
require that product discharge valves, "in addition to normal means, be 
closed by (1) an automatic heat-actuated means which will become effective 
at a temperature of not over 250° F, (2) a secondary closing means, remote 
from tank filling or discharge openings in event of fire or other accident." 
(49 CFR 178.341-5a.) 

Each compartment of the four-compartment tank on the Martin vehicle 
was equipped with a spring-loaded internal valve where the discharge 
piping began at the tank. The valves were opened manually and independently 
by a cable leading from each valve to levers in the control box. There were 
four levers in the control box — one for each of the four compartments. 
Unless the lever was set in the open position, holding the valve open by 
the cable attached, the internal valve would remain closed by the spring 
mechanism built into the valve. The cable from the valve to the opening 
lever was attached at the lever by a metal link held in place by metal 
nuts which were turned onto a threaded element of the linkage at the lever. 

In order to make the linkage fusible, as required by 49 CFR 178.341-5a, 
the inner cores (threaded portion) of the nuts securing the linkage 
to the lever were required to be made of a metal such as lead with a 
melting point of 250° F. If the lead melted, the tension of the linkage 
would be released and the internal valve would close automatically by 
its spring mechanism. This should automatically shut off the flow of 

After the accident, the linkages were intact, and the nuts on the 
linkage were found to be solid and nonfusible. It was not possible to 
establish when the nonfusible nuts were installed. 

Flames were under the trailer control box when the fire started. 
However, the automatic shut-off did not function because the linkage 
nuts were not fusible. Consequently, after the discharge hose burned 
through, the gasoline in the compartment being emptied continued to 
escape onto the ground under the trailer. Up to 400 gallons of gasoline 
from this compartment intensified the fire under the trailer. 

The firefighters found a large gasoline spill fire engulfing the 
rear of the trailer when they arrived on the scene. Closing the compartment 
valves with the remote control lever at the front of the trailer would not 
have affected the fire at that time. Gasoline continued to leak from the 
cracked valve at the storage tank and feed the fire, but the amount of fuel 
from this source was relatively small. 


Relaxation of Codes or Standards 

Corrective actions could be suggested to prevent occurrences 
similar to the Gadsden accident. However, safety codes and standards 

- 11 - 

already existed to control most of the events leading up to the fire and 
explosion, but these had not been implemented. (See Appendix C.) This 
indicates that the procedures for implementing these safety standards 
need to be improved. 

The NFPA and UL safety codes and standards are used by many States 
and private organizations to control risks in activities that are not 
otherwise regulated by Federal safety regulations, such as the storage 
of gasoline at a service station. For example, 30 States have adopted 
NFPA Code No. 30, which accepts storage tanks built in accordance with 
the UL 142-1972 for tanks and UL 79-1967 for pumps for flammable liquids. 
The UL-listing mark is widely used on manufactured products to represent 
that they are made in conformance with UL "standards for safety." The 
safety standards of both organizations can have widespread influence on 
gasoline transfer activities when they are recognized and implemented by 
States or municipalities. 

However, both the probability of an accident and its severity 
increase if a "recognized hazard" discussed in the code continues to 
exist at a facility. This was demonstrated by the accident and casualties 
at Gadsden, Alabama. 

Because of limited manpower in the State fire marshal's office and 
the service station's location in a sparsely populated area, the service 
station was not inspected. However, even if the Martin station had been 
inspected, the NFPA code would have allowed a relaxation of code require- 
ments for any noncomplying station features if the inspector did not 
consider the lack of compliance as a "recognized hazard to life or 
adjoining property." 

The Safety Board recognizes that there may be reasons for relaxing 
safety code requirements at specific service station facilities, although 
a "recognized hazard" should be eliminated to the extent possible. 
However, the NFPA does not define or otherwise explain what constitutes 
"recognized hazards," nor are there other published criteria by which to 
guide code inspectors. Without such guidance, the inspector's decisions 
reflect only the level of skill and individual experience of the inspector. 
Skills and experience of inspectors can vary widely, so the code is not 
uniformly administered, either within a jurisdiction or between jurisdic- 
tions . 

The Martin facility, though not in strict compliance with the code, 
remained in use, while the code was more strictly enforced within Gadsden, 
located only a mile from the accident site. This nonuniform application 
of the code affected the safety of the firefighters during the emergency. 
Since the off icers-in-charge were from Gadsden, a strictly enforced code 
area, they attacked the cargo tank fire assuming that the storage tank 
was adequately protected under the code. The firefighters, who could not 
adequately inspect this facility during the fire, continued to assume that 

- 12 - 

the aboveground storage tanks were adequately vented even when the vapor 
vent on storage tank No. 2 began to "whistle." Had they known of the 
lack of inspection or of the possibility of code variances, the firefighters 
might have used different tactics while fighting the fire. 

In effect, the firefighters safety was affected by their unawareness 
of the fire marshal's decision not to inspect the Martin facility against 
the fire code in the presumed minimum-risk area. There is no practical 
way for firefighters to identify uninspected facilities or safety code 
deviations and evaluate their effect while they are fighting a fire. 
Clearly, the effects should be examined beforehand. 

Many aboveground storage tanks are in use in many States. Estimates 
of the number of such tanks in service range as high as 18,000. Similar 
delivery risks can exist at any combustible storage facility which does 
not satisfy the provisions of the NFPA code. These risks will exist 
until code safeguards control "recognized hazards" or until the tactical 
consequences of relaxation of the code requirements are adequately 
conveyed to the local emergency personnel by the authority relaxing the 

The Safety Board has indications that risks due to unimplemented 
safety code requirements exist in other States but has not determined 
how widespread they are. Discussions with authorities in 19 States and 
with other knowledgeable persons disclosed that deviations from codes 
and standards frequently exist. For example, a representative from one 
State agency estimated that as many as half of the existing aboveground 
storage tanks in his State are not in strict compliance with the safety 
code. In another State, an estimated 20 percent of the tanks are not in 
strict compliance. Records describing the number of tanks subject to 
the safety codes or the status of their conformance with the code are 
not maintained or required under the code. However, dangers of the kind 
found at Gadsden, associated with unimplemented safety codes and standards, 
indicate a need to review code implementation at such facilities. 

UL "Standard for Safety No. 142" assumes that such tanks are "properly" 
installed and equipped. "Properly" is judged by the standards in the 
NFPA codes. Thus, if the NFPA code provisions are relaxed or otherwise 
waived locally, the impression that the equipment is safe because it is 
UL-listed becomes invalid. Furthermore, accountability for the safe 
performance of the equipment, usually viewed as resting with UL, the 
NFPA, and the installers when strict adherence to the rules is observed, 
logically must shift to those authorizing the waiver. Methods by which 
approving authorities may evaluate the safety effects of waivers are not 
routinely provided by UL or NFPA. This suggests that the codes might be 
improved for use by local authorizing officials by incorporating, in 
some appropriate manner, the safety concerns each standard is intended 
to control. 

- 13 - 

Maintaining Tank Vehicles to Safety Standards 

The safety standards most widely used to prescribe State safety 
requirements for tank vehicles carrying gasoline within a State are the 
dot's hazardous materials regulations 49 CFR, 100-178, and the NFPA 
"Recommended Regulatory Standard for Tank Vehicles for Flammable and 
Combustible Liquids," No. 385. For example, 10 States have adopted NFPA 
No. 385. Neither standard specifies how a State should verify the 
continuing conformance of a vehicle to the governing safety standards. 

When vehicles are not built or maintained to State Safety standards, 
risks increase. For example, when nonfusible nuts were substituted for 
fusible nuts on the unloading valve linkage on the tank vehicle, a 
condition was created which contributed to the severity of the Gadsden 
accident. This condition was not unique to the Martin gasoline vehicle. 
Safety Board investigators found nonfusible nuts on another gasoline 
tank semitrailer in a more recent accident. Significantly, the substitu- 
tion remained undetected before both accidents. Future design changes, 
such as the use of nonstandard threads for the fusible nut assembly, 
could reduce the likelihood of improper substitution of nonfusible nuts 
on these vehicles. However, periodic checks to verify that each vehicle 
continues to conform with all applicable safety codes and standards 
would still be required to detect noncompliance. 

It is not clear who, if anyone, in a State has the duty to verify 
the continuing conformance of a hazardous materials tank vehicle to 
governing State safety codes. Only one State, Connecticut has established 
a special periodic inspection program for hazardous materials tank vehicles 
under the code. Thus, opportunities exist for improving conformance with 
code requirements at the State level. For example, if an inspection report 
were required for hazardous materials safety equipment before the operator 
could renew his vehicle license, improved conformance over the life of the 
equipment would be achieved. 

UL-Listed Equipment — Misuse and Modification 

Safety risks are increased when UL-listed equipment is modified 
during installation in the field. The gasoline transfer pump used in 
this accident was listed for fixed installations. It was modified from 
its approved design when the portable power cord was connected to an 
open outlet box. The storage tank, as installed, did not conform to the 
codes. The improper use of equipment designed for transferring or storing 
bulk hazardous materials, such as gasoline, can contribute significantly 
to a serious accident, as was observed at Gadsden. The Board could not 
locate data to determine when or why the equipment was first misused or 
unsafely modified. At the time of the accident, the equipment still 
carried the UL "listing mark" to identify^ it as a UL-listed product 
produced under UL's followup service. However, when the equipment was 
misused and modified, the impression that the equipment was safe, normally 
conveyed by the UL-listing mark, became invalid. 

- 14 - 

UL acknowledges that many products investigated may cease to meet 
its standards because of misuse, failure to follow instructions or to 
inspect and maintain the product, or other changes after manufacture 
which affect the safety of the product. 

No methods for controlling such changes are currently prescribed by 
UL. No other generally accepted methods to control equipment modifications 
over the life of the equipment could be identified during this investi- 
gation. For equipment affecting gasoline delivery safety, many persons 
must be informed of the significance of such actions and given guidance 
for deciding when deviations from original UL-listed design are acceptable. 

Current approaches implicitly rely on codes, standards, or regulations 
to communicate this guidance. However, the absence of procedures to 
communicate the information to users of UL-listed products suggests that 
improved approaches are needed, particularly for small operators handling 
hazardous materials with limited resources and capabilities. Any listed 
equipment, to remain safe, should be maintained to the original design, 
or modified only by technically qualified persons who have been given 
proper guidance. Prohibiting deviations for other than its intended use 
probably would reduce accident risks, but may not be practical. While 
no specific means to control this equipment modification is obvious, the 
situation warrants further attention by standard-setting and regulatory 
organizations . 

The performance of the UL-listed tank in the Gadsden accident 
raises other concerns. In the fire, it ruptured violently. The known 
mechanisms for violent rupture of tanks are adequately understood so 
that they can be successfully countered by various technical means. For 
example, materials of construction might be changed. The aluminum cargo 
tank on the tank vehicle also ruptured, but it did not project fragments 
as the steel storage tank did when it breached. The comparative performance 
of the two tanks in the accident suggests that the UL "Standard for Safety 
No. 142" could be improved to provide safeguards against violent ruptures. 
These kinds of accidents also indicate that pressure relief devices cannot 
be relied on by firemen to protect tanks against violent rupture. Also, a 
method for providing protection against violent rupture should be found 
to protect tanks against explosions even when they are not installed 

Administrative Provisions in Safety Codes and Standards 

The above difficulties, viewed together, indicate that the administrative 
burden placed on State fire marshals under the safety codes and standards 
for gasoline transportation and the unloading and storage incidental thereto, 
is heavy. When this workload must compete with other duties, adverse safety 
effects can be significant, as was demonstrated at Gadsden. Administrative 
requirements, procedures, and capabilities should be analyzed when safety 

- 15 - 

codes and standards are developed, and again when they are adopted by 
individual jurisdictions. Apportioning the administrative tasks under 
safety codes and standards might result in increased conformance and 
reduced risks. For example, incorporating tank vehicle hazardous 
materials safety equipment inspection tasks into other State programs 
might overcome difficulties reported by fire marshal staffs in attempting 
to conduct vehicle inspections. 

The NFPA might wish to begin inquiring into the administration of 
its safety Standards by States if data available to it also indicates 
circumstances of the kind described in this report. 


The National Transportation Safety Board finds that: 

1. The absence of safeguards prescribed by NFPA safety codes in 
the Gadsden fire and explosion reflects a broader safety 
problem with nonuniform administration of these safety codes, 
rather than an enforcement problem. 

2. Nonuniform administration of State safety codes governing bulk 
storage and handling of NFPA Class I flammable liquids at 
service stations can adversely affect the safety of gasoline 
deliveries in intrastate and interstate transportation. 

3. When "recognized hazards" continue to exist at service station 
facilities, risks during unloading of gasoline and the proba- 
bility of injury to firefighters and bystanders during emergencies 
increases significantly. 

4. Uniform application of State safety codes governing bulk 
storage and handling of flammable liquids at service stations 

is impeded by the lack of guidelines for identifying "recognized 

5. Periodic verification of the continuing conformance of hazardous 
materials tank vehicles with hazardous material safety codes 
would reduce risks during gasoline unloading. 

6. The lack of a widely recognized or published procedure for 
discouraging misuse and unsafe modification of UL-listed 
equipment indicates a need to reexamine current methods 
relied on to prevent misuse and unsafe modifications. 

7. The UL "standard for safety" for aboveground storage tanks for 
Class I liquids could be improved to provide engineering 
safeguards, other than pressure relief devices, against violent 
ruptures and explosions in fires, particularly during bulk 
deliveries of Class I flammable liquids into such tanks. 

16 - 


Based on its special investigation and findings, the National 
Transportation Safety Board recommended that: 

— the Fire Marshals Association of North America: 

"Establish a program with the National Fire Protection Association 
to provide officials acting under Sections 1050 and 1060 of NFPA 
Code No. 30 with guidelines for identifying 'recognized hazards' 
at service station facilities, so that this code is applied more 
uniformly within the States. (Class II, Priority Action) (1-78-2) 

"Develop a procedure for identifying and reviewing the 'recognized 
hazards' at all gasoline service stations in which variances from 
NFPA Code No. 30 have been authorized to determine which service 
stations in a State constitute an unusual safety risk. (Class II, 
Priority Action) (1-78-3) 

"Develop a program to inform local firefighters of the unusual 
risks that exist at service stations where the code has been 
relaxed, so that firefighters may respond in the safest possible 
way to emergencies at such facilities. (Class II, Priority Action) 

— the American Association of Motor Vehicle Administrators: 

"Study ways in which States might assure periodic inspection of 
required hazardous materials safety equipment on tank vehicles 
which transport hazardous materials within a single State, and 
report its findings to the Safety Board within a reasonable time. 
(Class II, Priority Action) (1-78-5)" 

— the Underwriters Laboratory, Inc. : 

"Determine and adopt alternative ways to reduce the likelihood of 
misuse and unsafe modification of listed industrial products after 
their manufacture, with special emphasis on products that might be 
used in the transportation, storage, or transfer of bulk hazardous 
materials. (Class II, Priority Action) (1-78-6) 

"Review and amend UL 'Standard for Safety No. 142' for aboveground 
storage tanks for Class I liquids to protect against violent ruptures 
and explosions in fires involving such tanks. (Class II, Priority 
Action) (1-78-7)" 

- 17 - 
















February 24, 1978 

• - 19 - 



The National Transportation Safety Board wishes to acknowledge 
the generous cooperation and assistance of the State of Alabama Fire 
Marshal's Office; the National Fire Protection Association; the Bureau 
of Motor Carrier Safety of the Federal Highway Administration, U.S. 
Department of Transportation; the Martin Oil Company, Inc.; the 
Underwriters Laboratories, Inc., and numerous State officials during 
this investigation. 

- 20 - 


Flammable and Combustible Liquids Code 

NFPA No. 30— 1973 


10. Scope and Application. 


1050. In particular installations the provisions of this code may be 
altered at the discretion of the authority having jurisdiction after 
consideration of the special features such as topographical condi- 
tions, barricades, walls, adequacy of building exits, nature of occu- 
pancies, proximity to buildings or adjoining property and char- 
acter of construction of such buildings, capacity and construction of 
proposed tanks and character of liquids to be stored, nature of 
process, degree of private fire protection to be provided and the 
adequacy of facilities of the fire department to cope with flammable 
or combustible liquid fires. 

1060. Existing plants, equipment, buildings, structures and in- 
stallations for the storage, handling, or use of flammable or com- 
bustible liquids which are not in strict compliance with the terms 
of this Code may be continued in use provided they do not con- 
I stitute a recognized hazard to life or adjoining property. 

21. Installation of Outside Aboveground Tanks. 

2170. Drainage, Dikes and Walls for Aboveground Tanks. 

2171. Dr.mnage .\nd Diked Are.^s. The area surrounding 
a tank or group of tanks storing Class I, Class II or Class IIIA 
liquids shall be provided with drainage as in 2172, or shall be 
diked as provided in 2173, to prevent accidental discharge of 
liquid from endangering important facilities or adjoining property, 
or reaching waterways, except that in particular installations these 
provisions may be waived or altered at the discretion of the authority 
having jurisdiction when the tanks under consideration do not con- 
stitute a hazard to adjoining property. Tanks storing Class IIIB 
liquids do not require drainage or dikes. 

2172. Dr.mnage: \\'here protection of adjoining property' 
or waterways is by means of a natural or man-made drainage 
system, such systems shall comply with the following: 

(a) A slope of not less than 1 f>er cent away from the 
tank toward the drainage system shall be provided. 

(b) The drainage system shall terminate in vacant land 
or other area or in an impounding basin haNing a capacity not 
smaller than that of the largest tank served. This termination area 
and the route of the drainage system shall be so located that, if the 
flammable or combustible liquids in the drainage system are ignited, 
the fire will not seriously expose tanks or adjoining propierty. 

- 21 - 


(c) The drainage system, including automatic drainage 
pumps, shall not discharge to adjoining property, natural water 
courses, public sewers, or public drains unless the discharge of 
flammable or combustible liquids would not constitute a hazard, 
or the system is so designed that it will not permit flammable or 
combustible liquids to be released. 

2173. Diked Areas: Where protection of adjoining property 
or waterways is accomplished by retaining the liquid around the 
tank by means of a dike, the volume of the diked area shall comply 
with the following requirements: 

(a) The volumetric capacity of the diked area shall not 
be less than the greatest amount of liquid that can be released 
from the largest tank within the diked area, assuming a full tank. 
To allow for volume occupied by tanks, the capacity of the diked 
area enclosing more than one tank shall be calculated after deduct- 
ing the volume of the tanks, other than the largest tank, below the 
height of the dike. 

(b) Walls of the diked area shall be of earth, steel, con- 
crete or solid masonry designed to be liquidtight and to withstand 
a full hydrostatic head. Earthen walls 3 feet or more in height shall 
have a flat section at the top not less than 2 feet wide. The slope 
of an earthen wall shall be consistent with the angle of repose of 
the material of which the wall is constructed. Diked areas for tanks 
containing Class I liquids located in extremely porous soils may 
require special treatment to prevent seepage of hazardous quantities 
of liquids to low lying areas or waterways in case of spills. 

(c) Except as provided in (d) below, the walls of the diked 
area shall be restricted to an average interior height of six feet 
above interior grade. 

(d) Dikes may be higher than an average of six feet above 
interior grade where provisions are made for normal and necessary 
emergency access to tanks, valves and other equipment, and safe 
egress from the diked enclosure. 

(1) Where the average height of the dike containing Class I 
liquids is over 12 feet high, measured from interior grade, or where 
the distance between any tank and the top inside edge of the dike 
wall is less than the height of the dike wall, provisions shall be 
made for normal operation of valves and for access to tank roof(s) 
without entering below the top of the dike. These provisions may 
be met through the use of remote operated valves, elevated walk- 
ways or similar arrangements. 

(2) Piping passing through dike walls shall be designed to 
prevent excessive stresses as a result of settlement or fire exposure. 

(3) The minimum distance between tanks and toe of the 
interior dike walls shall be five feet. 

(e) Where provision is made for draining water from diked 
areas, drainage shall be provided at a uniform slope of not less 
than one per cent away from tanks toward a sump, drainbox 
or other safe means of disposal located at the greatest practical 
distance from the tank. Such drains shall normally be controlled 
in a manner so as to prevent flammable or combustible liquids 
from entering natural water courses, public sewers, or public drains, 
if their presence would constitute a hazard. Control of drainage 
shall be accessible under fire conditions and outside the dike. 



(f) No loose combustible material, empty or full drum 
or barrel, shall be permitted within the diked area. 

(g) Each diked area containing two or more tanks shall 
be sub-dixnded preferably by drainage channels or at least by inter- 
mediate curbs in order to prevent spills from endangering adjacent 
tanks within the diked area as follows: 

(1) \Mien storing normally stable liquids in vertical 
cone roof tanks constructed with weak roof-to-shell seam or ap- 
proved floating roof tanks or when storing crude petroleum in 
producing areas in any type of tank, one sub-division for each 
tank in excess of 10,000 bbls. and one sub-division for each group 
of tanks (no tank exceeding 10,000 bbls. capacity) having an 
aggregate capacity not exceeding 15,000 bbls. 

(2) ^^'hen storing normally stable flammable or com- 
bustible liquids in tanks not covered in sub-paragraph (1), one 
sub-division for each tank in excess of 100,000 gallons (2,500 bbls.) 
and one sub-division for each group of tanks (no tank exceeding 
100,000 gallons capacitv) ha\ing an aggi-cgate capacity not exceed- 
ing 150,000 gallons (3,570 bbls.). 

(3) WTien storing unstable liquids in any type of tank, 
one sub-division for each tank except that tanks installed in accord- 
ance with the drainage requirements of the Standard for \Vater 
Spray FLxed Systems for Fire Protection, NFPA No. 15, shall 
require no additional subdivision. Since unstable liquids will 
react more rapidly when heated than when at ambient tempera- 
tures, sub-di\ision by drainage channels is die preferred method. 

(4) The drainage channels or intermediate curbs shall 
be located bet^v■cen tanks so as to take fiJl advantage of the avail- 
able space with due regard for the individual tank capacities. 
Intermediate curbs, where used, shall be not less than 18 inches 
in height. 

2180. Tank Openings Other Than Vents for Aboveeround 
Tanks. * 

2181. Each connection to an aboveground tank through 
which liquid can normally flow shall be provided with an internal 
or an external valve located as close as practical to the shell of 
the tank. 


31. Materials for Piping, Valves and Fittings. 

3130. \'alves at storage tanks, as required by 2181 and 2342, and 
their connections to the tank shall be of steel or nodular iron except 
as provided in 3131 or 3132. 

3131. \'al\cs at storage tanks may be other than steel or 
nodular iron when the chemical characteristics of the liquid stored 
are not compatible with steel or when installed internally to the 
tank. AS'hen installed externally to the tank, the material shall 
have a ductility and melting point comparable to steel or nodular 
iron so as to withstand reasonable stresses and temperatures in- 
voKed in fire exposure, or otherwise be protected such as by ma- 
terials having a fire resistance rating of not less than two hours. 

T 23 - 


3132. Cast iron, brass, copper, aluminum, malleable iron, 
and similar materials may be used on tanks described in 2123 or 
for tanks storing Class 1 1 IB liquids when the tank is located out- 
doors and not within a diked area or drainage path of a tank 
storing a Class I, Class II or Class IIIA liquid. 

3140. Low metling point materials, such as aluminum, copper 
and brass; or materials which soften on fire exposure, such as 
plastics; or nonductile material, such as cast iron, may be used 
underground for all flammable and combustible liquids within 
the pressure and temperature limits of the ANSI B31, American 
National Standard Code for Pressure Piping,* if such materials 
are used outdoors in aboveground piping systems handling Class 
I, Class II or Class IIIA liquids or within buildings handling any 
flammable or combustible liquid, they shall b>e either; (a) suitably 
protected against fire exposure, or (b) so loacted that any leak- 
age resulting from the failure would not unduly expose persons, 
important buildings or structures or (c) located where leakage 
can readily be controlled by operation of an accessible remotely 
located valve or valves. 

34. Protection Against Corrosion. 

3410. All piping for flammable or combustible liquids, both above- 
ground and underground, where subject to external corrosion, 
shall be painted or otherwise protected. 


7110. General Provisions. 

7111. Liquids shall be stored in approved closed containers 
not exceeding 60 gallons capacity, in tanks in special enclosures as 
described in 7120, in aboveground tanks as provided for in 7115, 
or in tanks located underground as in 22. Vent pipes on tanks 
storing gasoline shall discharge only upward in order to disperse 
vapors. (Also see 7634 and 7635.) 

72. Piping, Valves and Fittings. 


7212. Piping shall be located so as to be protected from 
physical damage. 


Explosion p— ^ 

Station Under 
Fire Code 



Gate Valve 
Unproiected Agai 
Physical Damage 


isted Tank Di 
ing Capacity 


£ — mA" Struck Gate 

Believed Stai 
Satisfied Fin 

jcked Tn 
psed Stn 


Main Accident Events 

of Storage Tank 
Provided Pathway 
for Flame Front 

Defective Gate 
Valve Susceptible 

Enabling Factors 
I SI Addressed by Code Safeguards 

Tank Head Li 

Propelled At 
45 Angle 

\ I Defective Gate V jHont Head of \ ^ , ^. ^ \ 

\ Valve of Storage \ i-age Tank \ ^^J^ \ 

/ Irs-- r \^^_y i — r 

Combustion of 
Gasoline Vapor 
Containment Pr 
Rapid Pressure F 



Clothing did Not 
Protect Exposed 
Fire Fighters 







ilV E 










ed Threatened 


o Fight Fire 

Established Pcrinn 
of Evacuation Zo 


Figure 1C. Summary of Events and Enabling Factors, Gasoline Delivery Fire and Explosion |— ^ 

Gadsden, Ala. Aug. 31, 1976 

1? I c,.,..,'....,..i ^ I p.,....:„ — HI 

E - 




- > 





0I....IO, R«m.m.d 





rf"- ) 







40 (tall. 





- 27 - 


Public safety and emergency response personnel, safety code 
administrators and inspectors, bulk flammable hazardous materials 
carriers, facility designers and facility operators, safety and 
fire protection engineers, and technical safety committee members 
may find uses for this summary of "Events and Enabling Factors." 

It describes the main events leading to the explosion and 
fireball at the Gadsden, Alabama, accident on August 31, 1976, to 
show the factors that enabled each main event to occur, to display 
the factors addressed by existing safety codes and standards, to 
indicate factors that might be candidates for future revisions to 
safety codes and standards, and to aid emergency training and 
preplanning activities. 

Figure IC was prepared from information furnished to and developed 
by the Safety Board. This information is contained in the Safety Board's 
Public Docket HY-56-77. 

To use the chart which follows: 

1. Read the main events in the boxes along Line E, from "START" to STOP", 

This line displays the events that had to occur at Gadsden and the 
sequence they had to follow to produce the explosion and fireball , While 
many events occurred during the Gadsden accident, only a few main events 
led from the valve damage to the large losses in a direct proceed/follow 
sequence. Interruption of this flow of events at any point would have 
changed the outcome of the accident. 

2. For each main event, note the enabling factors above or below that 
event . 

These enabling factors must have existed 
for that event to occur. For example, the 
initial fire might have been controlled before 
the discharge hose burned through if the 
station operator or truck driver had had 
time to use a fire extinguisher; instead 
they were busy trying to extinguish the 
driver's burning clothing and attend to 
his injuries. Enabling factors which are 
addressed, in some manner, by NFPA or UL 
safety codes and standards are shown above 
the main events. Enabling factors not add- 
ressed by safeguards in NFPA or UL codes are 
shown below the main events. 


- 28 - 

3. Review the enabling factors which are addressed, in some manner, by 
NFPA or UL safety codes or standards. 

The relationship of the codes and standards 
to specific events in the Gadsden accident 
can be seen quickly on the chart . The 
effects of deviations from safety codes or 
standards on the course of events and the 
outcome can also be seen. The display 
can be used for examining the effects of 
relaxation of a code or standard require- 
ment, or for examining the effects of 
an alternative code or standard require- 
ment on this type of accident. 

4. Review the remaining enabling factors that are not addressed by 
safety codes or standards. These factors are potential candidates 
for treatment in revisions to codes or standards, or for voluntary 
action by anyone involved with bulk gasoline deliveries at service 
stations . 

Other events sequences could lead to most of the main events 
on the chart. For example, the fire that burned through the discharge 
hose in the Gadsden accident could originate and be fed by overfilling 
a storage tank during unloading in the vicinity of a different ignition 
source. Therefore, it might be desirable to develop an additional 
code or standard provision to require fire resistent discharge hoses, 
if this action is justified by analyses of other accidents. 

5. This chart can also be used to determine what actions might be 

taken to minimize losses during future emergencies of this type. 

For example, firemen or service station operators can identify numerous 

factors they should look for to diagnose the dangers requiring action 

in this type of emergency. They can also analyze the probable effects 

of various emergency actions on each main event, to support their training 

and preplanning activities. 












WibJ5-/.U li-/.D-/DA 

^ BOX 19518